Adam's Ordovician.

[Tidgy's Dad]

As well as Rostricellula minnesotensis, there are another three brachiopods that are the most common species in the Mifflin Member of the Platteville Formation. One of these is the fairly large orthid, Campylorthis defllecta. 

Here is one, again from Decorah, it is 3 cm wide, 2.6 cm long and the domed valve is a little over a cm deep. 

Notice how characteristically bumpy it is : 

And the very fine ribbing :

Thanks, Mike, it's lovely! @minnbuckeye

 

 

[doushantuo]

Nice!

[minnbuckeye]

Keep it up @Tidgy's Dad!!!!! I now can better ID my brachiopods. I better send you some more!

[Tidgy's Dad]

8 minutes ago, doushantuo said:

Nice!

Thanks, more photos added. 

[doushantuo]

bull26-01-02-115-132.pdf

Molluscan and brachiopod dominated biofacies in
the Platteville Formation (Middle Ordovician),
upper Mississippi Valley
PETER W. BRETSKY, SARA S. BRETSKY and PATRICK J. SCHAEFER

recommended,the Bretskys knew their Ordovician

1,436 MB

Bulletin of the Geological Society of Denmark,v26,1977

[Tidgy's Dad]

8 minutes ago, minnbuckeye said:

Keep it up @Tidgy's Dad!!!!! I now can better ID my brachiopods. I better send you some more!

Please do ! I love these beasties, many more of yours to post yet! 

[minnbuckeye]

10 minutes ago, doushantuo said:

 

Molluscan and brachiopod dominated biofacies in
the Platteville Formation (Middle Ordovician),

Nice article @doushantuo, can't find much as a lay person on my area so articles like this are MUCH appreciated.

[doushantuo]

Yah,know what you mean.

I noticed a pretty scarifying  absence of good reasonably recent regional geology literature,particularly as it pertains to the Paleozoic.

However:as I've said before :

the Paleozoic of the USA=>oil,gas,uranium,coal,underground CO2 storage,nuclear waste disposal

Might be that a lot of info is proprietary

[Tidgy's Dad]

On 12/6/2018 at 6:15 PM, doushantuo said:

bull26-01-02-115-132.pdf

Molluscan and brachiopod dominated biofacies in
the Platteville Formation (Middle Ordovician),
upper Mississippi Valley
PETER W. BRETSKY, SARA S. BRETSKY and PATRICK J. SCHAEFER

recommended,the Bretskys knew their Ordovician

1,436 MB

Bulletin of the Geological Society of Denmark,v26,1977

I hadn't read this one, probably because it was listed under Denmark.

Thanks a lot, it helps confirm the ids of Campylorthis deflecta and Rostricellula minnesotensis as well as the coral Lambeophyllum profundum. 

It also helps with the next specimen now I have returned from a two week fiddle with my Wenlock micro-matrix.

The most common fossil in the Mifflin is the orthid Pionodema conradi, so here is one, also from Decorah also thanks to marvelous Mike @minnbuckeye

This one's 2.2 cm wide, shows beautiful fine ribbing but is just the pedicle valve, unfortunately.

 
Nice. 

[Tidgy's Dad]

Same location and source : this is my oldest strophomenid. 

I think it's very unusual and lovely. 

This is Oepikina minnesotensis. 2 cm across the face of the valve.

Hmmm. Bad photo. 

Bu anyway, that's not the whole story, this is just the front of the valve, the flat face rolls into a domed back with beautiful ornamentation.

1.2 cm from the flat face to the rear of the specimen here. 

The brachial valve is missing but there is a nice gastropod, Hormotoma, I think in the matrix there, but more on that later. 

[Tidgy's Dad]

I finished Adam's Ordovician months ago having begun it over a year back, moved into the Silurian and thought I'd finish my Palaeozoic by the end of 2018. 

But i was wonderfully wrong! 

Thanks to the generosity of TFF members I'm still in the Middle Ordovician with a huge amount of stuff still to go. (mainly Upper Ord) 

But here in the Middle Ordovician Plattteville Formation, probably still the Mifflin Member, I present another Rostricellula minnesotensis, but this time from Grant County, Wisconsin, but still from the absolutely amazing Mike @minnbuckeye Happy New Year! 

Again, I've cleaned it with a pin. To some extent, anyway. 

 

 

oh dear, blurry pictures, let me clean the bits.

Anyway, this brachiopod is very slightly over 1 cm wide and high. 

 

 

[Tidgy's Dad]

And from the same source, Strophomena plattinensis. 

The darker one is slightly larger : 2.3 cm from tip to tip. 

[Tidgy's Dad]

This one is one of the most beautiful things ever. 

A little bit of cleaning up with my pin vice and the result is near perfect and over 450 million years old. 

Incredible. 

1.7 cm tip to tip, 1.5 cm the other direction and 7 mm deep/ high.

This is the wondrous Hesperorthis tricenaria.

This is one of my favourites ever! 

Thanks so much, Mike @minnbuckeye

[minnbuckeye]

@Tidgy's Dad, I don't even recognize those brachiopods. They cleaned up well!

 

 Mike

[Tidgy's Dad]

On 1/2/2019 at 8:37 PM, minnbuckeye said:

@Tidgy's Dad, I don't even recognize those brachiopods. They cleaned up well!

 

 Mike

Thank you, I'm really pleased with the way they've turned out. 

One or two could do with a little more time being spent on them, but i'm too eager to move on! 

You also sent me this hash plate, from the overlying Decorah Formation, Decorah, Iowa. 

I'm very interested in how the fauna changed over time and here we find the main part of this coquina are the broken pieces, or near complete shells of the orthid Pionodema subaequata, occuring in the place of P. conradi from the Platteville. Likewise, the large strophomenid here in the centre of this hash is Strophomena filitexta, whereas it's S. plattinensis  earlier. There are also bits of rhynchonellid which will most likely be Rhynchotrema laticosta or R. wisnonsinense where it was R. minnesotensis in the Platteville. 

The block is 10 cm across at its widest point.

Here is a closer shot of Strophomena filitexta, 3.2 cm tip to tip.

Here's a reasonable example of Pionodema subaequata, the species whose crushed remains make up a lot of this matrix. 1.3 cm wide. In the photo above you van see part of the hinge and inside of one right at the bottom of the frame. 

 

And here is a little fragment of the bryozoan Stictopora sp 5 mm long :

 

Another bryozoan, Batostoma? Bit of branch that's 2.3 cm long. 

And the reverse of the same hash plate showing crushed up bits of the orthids, mainly.

 

 

 

[Tidgy's Dad]

Here is a rather lovely pedicle valve of Strophomena filitexta free of the matrix. It is 3.2 cm wideand almost as long. 

These can be confusing as this looks like the outside of the valve but is actually the inside. The diamond shaped structure near the hinge was the attachment point for the muscles. This brachiopod had a convex brachial valve but concave pedicle valve. There are a few big strophomenids found in the Decorah Shale, but only Strophomena has this diamond shape muscle attachment structure. 

So here is the concave exterior of the same specimen :

And some detail. 

I had to be very careful when cleaning as they're very thin, maybe not too fragile but I was scared! 

There is another species of Strophomena found here, S.septata but it differs by having a median ridge.

Picture from "Equatorial Minnesota" website. 

 

[doushantuo]

Adam,love those brachs.

It has been shown by the French scientist Gaston Honore De La Farce(1852-1754) that is is beneficial to the mental health of human beings

to behold large pictures of orthids at least twice a week

[Tidgy's Dad]

3 minutes ago, doushantuo said:

Adam,love those brachs.

It has been shown by the French scientist Gaston Honore De La Farce(1852-1754) that is is beneficial to the mental health of human beings

to behold large pictures of orthids at least twice a week

Indeed, and I believe it was the Greek philosoper Socratotle  (4th century BAA) who said, " If I have learned but one thing in my life, it is that strophs are mighty cool." 

[Tidgy's Dad]

On page 2 of this thread, I was rather brilliant in my identification of a couple of species of rhynchonellid from the upper Middle Ordovician Cummingsville Formation of Rochester, Minnesota.

And I was looking at the information for the wrong formation so was completely brilliantly wrong! 

The two species of Rhynchotrema from this formation seem to be R. wisconsinense  and R. laticosta. 

R. wisconsinense is definitely a rounder form, but I can't seem to find a description of R. laticosta, so I'm guessing it's the broader, more highly ridged form.

Anyway, the point of this is that Doren @caldiggerrecently sent me some more, I've cleaned them up a little, but some of the matrix was very hard on these and i seem to have blunted several pins. Scale is in inches.(by mistake).

 

 

 

 

 

[Tidgy's Dad]

This one's a problem of nomenclature. 

It was known as Platystrophia biforata, but then Li and Copper 2006, seem to have renamed it Platystrophia biforatus.

Meanwhile, in the same year Zuykov and Harper released a paper showing the genus Platystrophia had been used as a 'bucket' taxon for orthids that looked like spiriferids, so divided it up based on the internal structure. So Platystrophia now applies only to some species from the  Baltic and other European areas. The North American ones were mostly placed into Vinlandostrophia, but this genus only includes species from the Upper Ordovician (Maysvillian and Richmondian). So species like Platystrophia biforatus, P. amoena and P. trentonensis from the Middle Ordovician have been rather left without a home. Indeed, Fossilworks lists P. biforatus in its unclassified section. 

Anyway, here from the Cummingsville of Rochester, Minnesota is "Platystrophia biforatus". 

Again, big thanks to Doren @caldigger

Some of the matrix on these was too tough to remove.

 

[Tidgy's Dad]

And also from the Cummingsville Fm. the lovely strophomenid Sowerbyella. Quite small for a strophomenid, very concavo-convex, but the concave dorsal valve doesn't really show up well in these photos. They're so concave that it almost looks like one valve. 

There are a couple of species found in this formation, S. minnesotensis  which tends to be smaller and more convex than S. curdsvillensis. 

Both these specimens fall within the size range of the former, but the profile shows the smaller one is much more convex, so maybe there's one of each here. 

The larger one :

 

 

 

View along the hinge line noting how it's quite flat shelled: 

The smaller specimen :

 And the hinge line showing a much more convex outline :

 

 

 

 

[Tidgy's Dad]

Now a trepostome bryozoan colony from the Upper Ordovician Georgian Bay Formation, Humber Member of Etobicoke Creek, Mississauga, Ontario, Canada sent to me by the amazing @Monica

There are a few candidates as to what it could be and without proper sections one cannot be certain, but i'm thinking this could be Mesotrypa distincta.

Colony is 3.8 cm across at it's widest point.

And the underside : 

Side view. The dome of the colony is a little less than a cm high. 

Close ups showing more details :

Lovely! 

 

 

[Tidgy's Dad]

Here's an interesting one. 

Here we have a bryozoan encrusting the shell of a straight-shelled nautiloid, most likely Treptoceras crebriseptum that I posted an example of earlier in this thread. 

This one is again from the Georgian Bay Formation of Etobicoke Creek and from kindly @Monica

The specimen is 7 cm long. 

With many of these bryozoans that are epibionts and encrusting cephalopods in the Cincinnatian, such as Atactopora and Spatiopora, the raised monticules are elongated and current-aligned, as they seem to be at least to some degree here. However, these genera don't seem to occur in the Georgian Bay Formation, or at least not the Humber Member. 

Genera that do occur in this formation include Atactoporella peculiaris which does have low monticules and is lobate with nodular protrusions,as can be seen here, plus Stigmatella personata lobata and S. vulgaris, the former having low rounded quite large monticules and the latter usually growing around something like a crinoid stem. None of these seem to have been mentioned as growing around orthocerids. 

Interesting, the cephalopod is quite flattened and shows a lot of encrustation on the edge above but not on the one below. Could it have died and whilst lying with one edge upwards in the substrate have been colonized then? With all those bumps and nodules, the poor cephalopod wouldn't have been very streamlined if it were swimming.

Here is a close up of the zooecia :

To me it seems most like Stigmatella personata lobata, but I'm really not certain without detailed sections.

To further muddy the waters there is a species of stromatoporoid, Dermatostroma scabrum that does encrust Treptoceras in the Georgian Bay Formation, see Plate .3, number 17 in   http://webcentral.uc.edu/eprof/media/attachment/eprofmediafile_662.pdf. But his appears to be quite thin, not nodular and there are hollows in the centre of the papillae.

 

 

 

 

 

 

 

  

[Tidgy's Dad]

And from the same location, a couple of seemingly current orientated Treptoceras crebriseptum :

(the longest one is about 8 cm exposed length.)

It has some of the Georgian Bay Formation's bivalves on the back. 

Thanks again,  @Monica

 

[Tidgy's Dad]

Also from the same Formation from marvelous @Monica but from the Mimico Creek in the Toronto area is this lovely little brachiopod positive and negative.

It's one of surprisingly few brachiopods found in the formation and most of those that can be found occur in the shallower waters of the coral and bryozoan rich reefs of the Credit Member. 

Only 7 mm across it looks very like Zygospira modesta, which does occur in the Georgian Bay Formation, but I can't find it recorded at Mimico or Etobicoke Creeks. But 'Zygospira erratica' is recorded at Mimico Creek (not Etobicoke, though). This species has finer costae and a deep sulcus which can't be seen here, though the fold does seem to be a bit raised. And I'm not sure if this species has now been reassigned to Catazyga erratica anyway. though seems different to me. @Peat Burns

The piece also has various bits of bivalve on the back.